The present invention is generally related to the field of communications relating to an inground device and, more particularly, to an inground device with advanced transmit power control and associated methods.
While not intended as being limiting, one example of an application which involves the use of an inground device or transmitter is Horizontal Directional Drilling (HDD). The latter can be used for purposes of installing a utility without the need to dig a trench. A typical utility installation involves the use of a drill rig having a drill string that supports a boring tool, serving as one embodiment of an inground tool, at a distal or inground end of the drill string. The transmitter is generally carried by the boring tool. The drill rig forces the boring tool through the ground by applying a thrust force to the drill string. The boring tool is steered during the extension of the drill string to form a pilot bore. Upon completion of the pilot bore, the distal end of the drill string is attached to a pullback apparatus which is, in turn, attached to a leading end of the utility. The pullback apparatus and utility are then pulled through the pilot bore via retraction of the drill string to complete the installation. In some cases, the pullback apparatus can comprise a back reaming tool, serving as another embodiment of an inground tool, which expands the diameter of the pilot bore ahead of the utility so that the installed utility can be of a greater diameter than the original diameter of the pilot bore.
Steering of a boring tool can be accomplished in a well-known manner by orienting an asymmetric face of the boring tool for deflection in a desired direction in the ground responsive to forward movement. In order to control this steering, it is desirable to monitor the orientation of the boring tool based on sensor readings obtained by sensors that form part of the transmitter carried by the boring tool or other inground tool. The sensor readings, for example, can be modulated onto a locating signal that is transmitted by the transmitter for reception above ground by a portable locator or other suitable above ground device. In some systems, the transmitter can couple a carrier signal modulated by the sensor readings onto the drill string to then transmit the signal to the drill rig by using the drill string as an electrical conductor. One class of prior art transmitters is battery powered. It should be appreciated that an inground operation is generally adversely affected by draining the batteries to a degree that renders the transmitter as inoperable, resulting in the need to enter a time consuming process to trip the transmitter out of the ground simply to replace the batteries. The prior art has adopted a number of different approaches in order to attempt to address concerns relating to transmitter battery life. One approach resides in the use of higher capacity batteries. While higher capacity batteries are generally higher in cost, a greater limitation may reside in the higher capacity battery having a physical outline and/or characteristic voltage that is incompatible for installation in a given transmitter. Another approach taken by the prior art resides in reducing transmitter power consumption in order to extend battery life. Of course, this approach reduces transmitter output power and invokes the competing interest of limiting transmission range, which can be of limited value when the inground operation is being performed at relatively high depths and/or range. Still other approaches are described hereinafter, however, each of these approaches is recognized as introducing associated limitations.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.